This invention relates to a side airbag arrangement for motor vehicles having a plurality of airbags and, in particular, to an arrangement in which the side airbags, when activated, unfold substantially vertically downwardly.
Side airbag arrangements which are activated in the case of a collision to form a cushion between the vehicle occupant and neighboring vehicle door or side wall are known. Such airbag arrangements are usually mounted in the region of the roof frame and take up only very little space in the nonactivated state.
Side protection airbag arrangements are disclosed in U.S. Pat. No. 2,834,606 and U.S. Pat. No. 3,897,961. Pat. No. 2,834,606 describes airbags which, in the initial state, are folded together and extend above each side window in the longitudinal direction of the vehicle and, in the event of a collision, expand in the downward direction until they are in positions next to the feet of the vehicle occupant. U.S. Pat. No. 3,897,961 relates to so-called inflatable side curtains which, in the activated state, extend from a region of the roof frame downwards to below the bottom of the window of the side door. These curtains are subdivided by vertically running seams into a plurality of airbags.
German Offenlegungsschrifft No. 15 55 142 also describes an occupant side protection arrangement having a plurality of inflatable protective elements which are fastened to the upper edge of a window frame and, in the case of a collision form a lateral safety wall.
U.S. Pat. No. 4,966,388 relates to an occupant side protection arrangement having airbags which, in the state of rest, are accommodated in a vehicle door and, when activated, emerge in the upward direction from a flap which opens and are then attached to a region of the roof frame and to the vertical pillars adjacent to the window of the vehicle by touch-and-close fasteners. However, the upwardly expanding movement of the airbag below the window is disadvantageous to the extent that a the vehicle occupant often has one arm on an armrest or, especially when the side window is open, on the bottom of the window frame so that the expansion path of the airbag is not free.
In the case of those side airbag arrangements, the cushion formed by the airbags in the event of a collision assumes an undefined position and shape.
German Offenlegungsschrifft No. 43 07 175 discloses an occupant side protection airbag arrangement which is formed by interconnected airbags which, in the nonactivated state, are accommodated at least partially in a folded-together fashion in a region of the roof frame of the vehicle above a side window and, in the activated state, extend in front of the side window as a cover projecting downwardly from the region of the roof frame.
In this case, the airbags are disposed with their longitudinal axes essentially vertical, and an airbag intended to cover the window pillar is connected to the pillar by a guide in the manner of a roller guide, so that the cover formed by the airbags is fixed at one end in the horizontal direction. Each of the airbags is connected to a separate gas generator and it is possible for the activation of the gas generators to be initiated either simultaneously or else at successive times.
In the inflated state, the airbags cover the region of the side wall of the motor vehicle close to the head.
However, this arrangement is complex because the number of gas generators corresponds to the number of airbags. If, on the other hand, the cushion is formed by a smaller number of airbags, in the extreme case only one airbag, there is the risk that the cushion will be compressed too severely when acted upon by a local impact from the occupant because the gas can be displaced into the regions not acted upon with the result that the protective effect is reduced.
Furthermore, European Patent Publication No. 0 685 366 discloses a knee cushion for knee impact protection which has a plurality of interconnected airbags arranged next to each other, each of which is connected by a one-way valve to an upstream chamber connected to a gas generator. When the gas generator is activated the chamber is filled with gas and each airbag is filled with gas from the chamber so that the gas pressure in the airbags corresponds to that in the chamber. If the gas pressure in one airbag exceeds the pressure in the chamber as a result of compression of the airbag caused by a vehicle occupant impacting it, the one-way valve closes so that the gas can no longer escape from the airbag. The arrangement of a plurality of airbags each connected to an upstream chamber in this manner provides a strengthening of the knee cushion and better knee impact protection, since smaller chambers are pressured with the gas and the gas can be displaced far less from a local area which receives an impact than with a single chamber larger airbag.